Nearly 3 billion dry-cell batteries are purchased every year in the United States. In order to reduce the number of these that end up in landfills, efforts have been made to push both the use of rechargeable batteries and the recycling of disposable batteries. Recovery of battery materials via recycling can also provide cost benefits in battery production compared to producing batteries using all new material (Sayilgan 2009). As the demand for batteries containing recycled materials increases, the need for more efficient recycling processes also increases.
Processes for recycling batteries are described in U.S. Pat. Nos. 8,728,419 and 8,911,696, both to Smith et al., as well as Ferella et al. (2010), which are hereby incorporated by reference in their entirety. A variety of other chemical and/or mechanical methods for recovering metals, and particularly manganese (Mn) from discharged batteries, are known in the art. Among the types of batteries that comprise recoverable manganese are alkaline batteries, in the cathode, and zinc carbon batteries, in the interior of the battery, adjacent to the anode. The recovered manganese can be used to make electrolytic manganese dioxide (EMD). The recovered manganese may have impurities, including potassium (K) and zinc (Zn), which reduces the utility of the recycling process. For example, recycled cathode manganese recovered from alkaline batteries inherently has high levels of potassium due to the potassium hydroxide (KOH) electrolyte in the cell and high levels of zinc from cross-contamination of the anode. While many methods focus on the separation of the zinc, very little effort is focused on removal of potassium. Current mechanical and thermal recycling processes are ineffective at removing potassium. Potassium negatively impacts the regenerated EMD performance, quality, and costs. This reduces the efficiency of using the recovered manganese to produce EMD for use in batteries comprising recycled content. In turn, this makes it difficult to produce batteries comprising a higher percentage of recycled manganese (“higher recycled content” or “higher content”).
Consequently, a need for a more efficient process for obtaining and purifying recycled material from discarded alkaline or zinc carbon battery feedstock exists. In particular, a system that reduces the amount of potassium and zinc impurities, and/or increases the amount of recovered manganese, would be welcomed. A method of reusing water used during the recovery process, so as to produce less waste water in the course of recycling, would also be welcomed.